Engine catalyst diagnostics may be used to determine whether a catalyst is sufficiently functioning to reduce exhaust gas emissions. Various approaches may be used to identify the catalyst system performance, such as model based approaches, fuzzy logic, etc.
In the various approaches that have been used, there has often been a tradeoff in terms of the amount of “training” data needed, calibration required, and the level of diagnostic accuracy required (e.g., false positive, undetected degradation, etc.). Furthermore, these techniques have often required extensive windowing functions, where data from only selected operating conditions are considered, such as certain speed/load points, steady state operation, etc.
The inventors herein have recognized the issues with the above approach and provide a method to at least partly address them. One example embodiment includes a method of monitoring catalyst performance. The method comprises applying a set of parameter readings for a given sample to a support vector machine to generate a classification output, recording a plurality of classification outputs for a plurality of successive samples over a first duration, and indicating catalyst degradation if a threshold percentage of the classification outputs indicates degraded catalyst performance.
Support vector machines applied to catalyst diagnostics provides the unexpected benefit of simplified calibration, high accuracy, and modest training requirements. Also, as most of the computation is involved in model training, which is an offline process, it is possible to obtain improved real-time implementation with reduced computational requirements.
In one example, the support vector machine classifies a data set by building a hyper-plane that separates the data into two separate classes. The optimal hyper-plane is selected in such a way as to maximize the margin (the distance between the points in either class to the hyper-plane). Further, the support vector machine approach using a linear classification can be extended to non-linear systems by first transforming the original feature space into a higher dimension where the data can be linearly classified, and then building a linearly separable hyper-plane in the transformed dimension. Through the appropriate selection of a transformation function, the proposed approach enables an improved catalyst diagnostic approach to identify degraded catalyst operation with non-intrusive monitoring and simplified calibration, and with significantly reduced windowing. It may be noted, as the classification is carried out for each instance of time, the proposed approach can provide faster data analysis that those in which data is first windowed, before it is analyzed.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.